Decontamination of sub-systems of LWR plants has now become relatively common in the United States, and is widely recognized as a useful contributor to the reduction of radiation exposure of workers at these plants. Sub-system decontamination involves exposing a part of the reactor circuit to chemical solutions which dissolve the radioactive deposits which have accumulated on the process equipment, including piping. The spent decontamination solutions are then treated by ion exchange to retain all of the chemical and radioactive burden of the decontamination solution on the resin, while clean water is returned to the system. LOMI is but one example of a sub-system decontamination process having these characteristics.
In prior art decontamination solution recovery systems, the ion exchange resin normally consists of cation resin which carries the majority of the radioactive burden, and anion resin which carries the anionic components of the decontamination process chemicals. Fully loaded ion exchange resins are normally managed by dewatering or solidification in cement-based matrices, for shipment off site to an appropriate burial location. Since ion exchange resins have a relatively limited retention capacity for radioactive cations and organic anions, a relatively high mass of the material sent for disposal and burial is the ion exchange resin itself and its binding matrix as opposed to the captured chemical burden. It would therefore be desirable to have a waste treatment process for decontamination solutions which will isolate the radioactive burden in a more concentrated solid matrix than is presently achieved with routine ion exchange resin. Furthermore the anionic components of decontamination process solutions are normally non-radioactive organic acids which could in principle be converted to harmless gaseous products not requiring treatment as radioactive waste. This approach to the management of the anions present in the decontamination solutions would serve to reduce the amount of ion exchange resin requiring burial.
Presently, decontamination process reagents are normally used in a "once-through" manner, that is the manufactured chemical is added to the decontamination process circuit. Subsequently, the process reagents are removed for disposal along with the radioactive species captured on the ion exchange resins. Since these decontamination reagents are used nondestructively in the decontamination process and are not substantially altered or consumed to any significant extent during decontamination, it is therefore desirable to use, recover, recycle and reuse these decontamination reagents for several decontamination cycles.